The present invention relates to a wiping apparatus for wiping excess ink left on an intaglio printing surface in an intaglio printing machine.
An intaglio printing machine is known as one type of a rotary printing press. FIG. 1 is a schematic side view showing a conventional intaglio printing machine. Referring to FIG. 1, sheets 1 stacked on a feeder 2 are fed by a suction mechanism therefrom one by one. A feedboard 4 and a swing mechanism 5 are arranged between the feeder 2 and a printing unit 3 located in front of the swing mechanism 5. The feedboard 4 receives each sheet 1 fed from the feeder 2 and adjusts a printing timing. The swing mechanism 5 grips the sheet 1 and swings to transfer the sheet 1. The printing unit 3 has an impression cylinder 9. Three gripper units (to be referred to as grippers hereinafter) 8 each comprising grippers 6 and gripper pads 7 are mounted on the outer surface of the impression cylinder 9 at equal angular intervals. A plate cylinder 10 having substantially the same diameter as the impression cylinder 9 and transfer and delivery cylinders 11 and 12 having diameters substantially 1/3 that of the impression cylinder 9 are brought into rolling contact with the impression cylinder 9 at different positions. Grippers (not shown) the same as the grippers 8 are mounted on the transfer cylinder 11 to transfer the sheet 1 from the swing unit 5 to the grippers 8 of the impression cylinder 9. A pair of right and left delivery chains 13 are looped around sprockets coaxial with the delivery cylinder 12 and corresponding sprockets (not shown), respectively. Delivery grippers are mounted on the delivery chains 13 to receive the sheet 1 from the grippers 8 of the impression cylinder 9 and feed it. An intaglio plate constituted by a flat surface and recesses as a printing image is mounted on the outer surface of the plate cylinder 10. A plurality of form rollers 14 are in rolling contact with the intaglio plate. Duct rollers 16 which are rotated in ink ducts 15 are in rolling contact with the form rollers 14, respectively. Ink flows from the ink ducts 15 are formed into uniform ink layers by vibrating rollers 17 which are in rolling contact with the duct rollers 16, respectively. A wiping roller 20 in a cleaning liquid tray 19 is in rolling contact with the oblique lower portion of the plate cylinder 10. It should be noted that the wiping roller 20 is rotated in the same direction indicated by the arrow as the plate cylinder 10.
In the conventional intaglio printing machine having the arrangement described above, inks of three colors are delivered by the duct rollers 16 from the ink ducts 15 and uniform ink layers are formed by the vibrating rollers 17, respectively. Thereafter, the three inks are coated on the surfaces of the form cylinders 14, respectively. In this case, the inks are applied to both the recesses of a printing area and the flat surface of a nonprinting image area. A cleaning liquid 18 is supplied to the flat surface of the plate through the wiping roller 20. Since the plate surface and the outer surface of the wiping roller 20 move in opposite directions at their contact point, ink is removed from the nonprinting area and left only in the printing area. Since a large pressure of 1 ton/cm.sup.2 acts on the sheet 1 between the cylinders 9 and 10 during feeding of the sheet from the transfer cylinder 11 to the delivery chains 13 through the impression cylinder 9, inks in the recesses are transferred to the sheet 1, thereby performing copperplate printing.
There are two types of wiping systems in conventional intaglio printing machines: solvent type wiping; and water-soluble type wiping. Solvent type wiping is performed using mainly trichloroethylene, which is toxic to the human body. For this reason, since an organic solvent is difficult to handle, water-soluble type wiping has recently been widely used. According to this wiping system, an aqueous solution of sodium carbonate, Turkey red oil and a surfactant is used as the cleaning liquid 18. The removed ink is mixed with the cleaning liquid 18, and the mixture left on the outer surface of the wiping roller 20 is washed off by a brush or an abrasive resin material which is disposed in the cleaning liquid tray 19. However, such a conventional wiping apparatus has the following drawbacks.
Even though water-soluble type wiping is nontoxic, it is difficult to dispose an organic material contained in the cleaning liquid after washing. Currently the organic material is burned for their disposal. However, when water is burned or boiled and vaporized, much energy is wasted. In addition, the composition, temperature and so on of the cleaning liquid directly influence the quality of the printed products, so that a liquid circulating function and a temperature control function are required. These additional devices increase the overall cost of the printing machine. A mixture of the cleaning liquid 18 and the removed ink is precipitated like a sludge, which contaminates the cleaning liquid 18 or changes its composition. Furthermore, the quality of printed products is degraded, and need for replenishment of the liquid degrades work efficiency. Additionally, ink applied to nonprinting areas and removed by the wiping roller 20 cannot be used again, thereby wasting a large quantity of ink.